Guide for mechanical guiding of a catheter in connection with cardio and vessel examination

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Patent Office

SWEDEN (19) SEE

C12) PUBLISHING WRITING [B1 (2i)

8603304-0 (51) International class * Ä61B

5/02 (44) Application outsourced and publication date published (41) Application widely available (22) Patent application filed (24) Maturity date (62) Application number (86) International filing day (86) Filing date for European patent application (30) Priority information ( 11) Publication __. _

88-03-28 number 454 045

88-02-05

86-08-04 Ångman income as:

86-08-04

El Swedish patent application

C completed international patent application with number □ converted European patent application with number

<td> (71 )</td><td>Applicant</td><td colspan="2">Radisensor AB, Kungsgatan 70 753 21 Uppsala SE</td>

<td> (72)</td><td>Inventor</td><td>1) L. Tenerz, 2) B. Höök, 3) T. Engstrom 2) Västerås</td><td>, 1.3) Uppsala,</td>

<td> (74)</td><td>Agent</td><td>Brann</td><td></td>

<td> (54)</td><td>Name</td><td colspan="2">Conductor for mechanical control of a catheter during cardiovascular examinations</td>

<td> (56) (57)</td><td colspan="2">Published publications: US, A 3 946 727 (US, C1 128.4), US, A 4 US, A 4 329 98O (US, C1 128.4), US, A 4 487 2O6 (US, C1 128,667) Abstract:</td><td>274 423 (US, C1 128,675),</td>

The invention relates to a conductor for the mechanical control of a catheter in cardiovascular examinations. The conductor comprises a miniaturized pressure sensor (1) which is disposed at the distal end of the conductor. The conductor further comprises a ventilation duct (4, 15) intended to connect the pressure sensor to ambient atmospheric pressure.

DB 847209

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The numbers in brackets indicate international identification code, INID code. Letters in clamps indicate international document code

454 045

In X-ray examinations of the cardiovascular system, so-called catheters, ie. thin plastic hoses, in several ways. Through the catheter, contrast fluid can be injected to make parts of the vascular system visible upon exposure to X-rays. Blood samples can be taken for analysis of dissolved gases, pH, ion concentration, etc. Hydrostatic pressure can be measured with a pressure sensor connected to the catheter.

However, catheters are not only used for diagnostic purposes. A new form of treatment for vasoconstriction, utilizes catheters that are expandable by applying strong hydrostatic pressure in a cavity, so-called balloon catheters. Furthermore, pharmaceutical preparations can be injected through catheters to achieve a local action.

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In order to reach the end of the catheter to the desired location in the cardiovascular system, a so-called conductor is used which is wired and with a dimension which allows its insertion into the catheter. Typical dimensions of catheters are outer diameter 1-3 mm, inner diameter 1

0.5-1.5 mm, and length 80-150 cm. The conductor diameter may be |

0.5-1.0 mm. While the catheter is made of polymeric material, the conductor is often composed of metallic materials, often stainless steel. jl

When measuring pressure with known devices, the pressure is transferred hydraulically in the catheter. This is problematic because of the transfer characteristics of the catheter / pressure sensor system.

In addition, microscopic air bubbles can significantly degrade&gt;

transfer. Thus, this measurement is not reliable;

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The present invention solves this and related problems by means of a miniaturized sensor, whose signal transmission is by optical means via an optical fiber embedded in the conductor, which sensor Sr is mounted near the distal end of the conductor (the end of the probe located closest to the test site). ). Through

454 Due to the small dimensions made possible by the fiber optic technology, the conductor can be given such mechanical properties in the form of bending and torsional stiffness, as well as such malleability, which is required for its function to guide the catheter to the test site in the cardiovascular system. The optical signal transmission is not affected by the defects in the transmission that the hydraulic principle possesses. In addition to more secure diagnostic measurement values, simpler handling is provided. Through the extremely small dimensions of the pressure sensor and the conductor, pressure measurements can be made at points in the cardiovascular system that were previously inaccessible.

The features of the invention are apparent from the appended claims.

In the following, a preferred embodiment of the invention will be described in connection with the figures, in which Fig. 1 shows a principle embodiment of the conductor according to the invention with some parts broken away, and Fig. 2 shows a detail of a particular embodiment.

The pressure sensor 1 (Fig. 1) is located near the distal end of the conductor

2nd Within the scope of what is possible to achieve with fiber optic technology and micromechanics, a variety of detailed designs of the sensor are conceivable, for example the one described in the Swedish patent application 8602836-2. The optical fiber 3 extends along the entire length of the conductor and passes at the proximal end of a connector 9. By this, the fiber 3 can be connected to another fiber or arrangement of light source and light detector with negligible optical losses. The pressure sensor 1 is mechanically connected to a jacket 5, in the depicted embodiment consisting of a spirally wound metal wire. The conductor in this section then becomes easily flexible and elastic, which is necessary to avoid the risk of perforation of the walls of the blood vessels when the conductor is inserted. The flexible portion is usually 5-20 cm long and extends towards the proximal end i

454 045 a stiffer part. This may consist of a denser coiled wire, thicker and thus stiffer or, as shown in Fig. 1, a thin-walled metal tube. The transition 8 between the easily flexible and rigid part can be abrupt or gradual. An advantage from the reliability and safety point of view is if the parts 5, 6 and 8 are made of a single piece of metal by mechanical machining, etching, molding in other ways etc. The distal end of the pressure sensor is connected to a further section of a splice-shaped wire by means of a weld joint 10 or by soldering. The jacket 5, 6 is surrounded by a thin-walled hose 12 of polymer material (polyethylene, fluoropolymer, silicone or polyurethane). The thin-walled hose is shrunk over the coil in the joint region 21 between the pressure sensor 1 and the end portion by, for example, heating. This end portion will thus become even more flexible, which is necessary so that the conductor does not cause damage to the sensitive tissue in blood vessels and the like. Of course, this end portion should also be heparinized. Conveniently, the distal end 2 of the conductor is rounded and in the region of the pressure sensor the conductor is provided with a sealing surface 16 for calibration purposes, (see Swedish patent SE-441 725).

A characteristic characteristic of the conductor and of its function which is very important is that between the fiber 3 and the metal tube 6 there is a space 7, which forms a ventilation channel for the pressure sensor 1. If the pressure sensor 1 is adapted to detect relative pressure variations, then a reference pressure, which is suitably constituted, is required. of the prevailing air pressure. Thus, in the easily flexible part, a ventilation duct is formed by surrounding the jacket 5 by the thin-walled hose 12. The space 4 then forms a pressure connection extending from the pressure sensor via the channel 7 and the hole 17 into the surrounding atmosphere. It is important to note that the pressure transmission takes place via air present in the conductor, which provides a safer connection than if the transmission were to be done hydraulically via, for example, water.

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The thin-walled hose 12 constitutes the material exposed to the body fluid. In order to improve the biocompatibility of the material, ie. adaptability to the biological medium, the polymeric material in the tubing can be coated with a thin film of a material with good tissue acceptance, e.g. heparin.

In the rigid conductor portion, the thin-walled hose can be replaced with a possibly heparinized polymer coating 11.

Fig. 2 shows an alternative detail design of a short section of the conductor according to the invention. The jacket in this case consists of two cross-twisted metal strips 13, 14. This embodiment provides high torsional stiffness in combination with a relatively good flexibility, which can advantageously be used in controlling the conductor over vessel branches and sharp bends. In this case, the ventilation duct consists of a thin capillary tube 15 which runs parallel to the optical fiber 3.

The jacket 5, 6, 13, 14, the fiber 3, the hose 12 or the coating

II preferably contains a compound, for example, an oxide, of some heavy metal, for example tungsten or bismuth, so that the conductor is thus visible during X-ray exposure.

Those skilled in the art will appreciate that the invention can be modified in many ways within the scope of the appended claims.

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